(a) Field of the Invention
This invention relates to novel pyrimido[1,6-a]indole derivatives, to therapeutically acceptable salts thereof, to processes for their preparation and to pharmaceutical compositions of the derivatives.
More specifically, the present invention relates to novel pyrimido[1,6-a]indole derivatives having a substituted ethyl group at position 5 and optionally being further substituted at various positions on the pyrimido[1,6-a]indole nucleus. These derivatives are useful as antihypertensive agents at dosages which do not elicit undesirable side effects.
(b) Description of the Prior Art
Only a limited number of reports dealing with compounds having a pyrimido[1,6-a]indole nucleus are available. More specifically, the reported pyrimido[1,6-a]indoles are substituted at positions 5 and 7 with a methyl group, see L. N. Borisova et al, Khim. Geterotsikl. Soedin., 645(1972) cf. Chem. Abstr., 77, 139850 k (1972), and C. J. Cattanach et al., J. Chem. Soc. (c), 359(1971). Other pyrimido[1,6-a]indole derivatives are also known; for example, 2,5-dimethyl-1,2,3,4-tetrahydropyrimido[1,6-a]indole derivatives and 2,5-dimethyl-4a,5-dihydropyrimido[1,6-a]indole derivatives are reported by G. N. Artemenko et al., Farmakol. Toksikol, 39, 651 (1976), cf. Chem. Abstr., 86, 37493 q (1977), to have antidepressant activity.
The compounds of the present invention are structurally different from the prior art compounds by having a substituted ethyl group at position 5 of the pyrimido[1,6-a]indole ring system.